neuro230 final exam review

raphe nucleus

• manufactures serotonin

• lesion results in temporary insomnia

• microinjection of serotonin into raphe triggers sleep

mechanisms of barbituates and benzodiazapines

• sleeping pills

• promote GABA signals

• GABA = inhibitory

• inhibits neurons that would otherwise arouse and promote waking

lateral hypothalamus and waking

hypocretin neurons here promote waking (ex. narcolepsy = missing hypocretin neurons)

cerveau isole

• transection at superior colliculus

• isolation of forebrain from brainstem = permanent sleeping

• shows arousal generated by upper brainstem

lower pre-trigeminal transection

• permanent wakefulness

• sleep generated in lower brainstem

hypovolemic thirst

loss of blood volume (ex. bleeding, perspiration) *note: is NOT turned on by eating salt and raising blood pressure

hyperosmotic thirst

caused when osmotic detector neurons in LH triggered by over-retention of salt

renin

secretion by kidney during hypovolemic thirst

angiotensin ll

renin enzyme cleaves angiotensinogen in half → _____ is signal that goes to brain to cause thirst

aphagia

inability to feel hunger sensation

lateral hypothalamus and aphagia

selective lesions in rat → rats did not eat

LH neuron lesion

excitotoxin mimics glutamate, overexcitation, leads to aphagia

LH fibers of passage lesion

(fibers = mesolimbic, ascending from midbrain) leads to aphagia

hyperphagia

uncontrollable overeating

ventromedial hypothalamus (VMH) lesion

• leads to hyperphagia

• hyperinsulinemia, gain weight even if eating the same amount of food

• oversensitive to both pleasant and unpleasant tastes (yum = extra yum, gross = extra gross)

leptin

• produced by adipose (fat) cells, signals satiety

• acts on arcuate nucleus to inhibit hunger

• more fat cells = more leptin in bloodstream

ghrelin

• secreted in stomach lining to send hunger signal

• levels typically rise before meals and fall after, reflecting body’s circadian rhythm for feeding

paraventricular nucleus

• norepinephrine pathway

• lesion = hyperphagia

• NE agonists = diet drugs

• serotonin signals = suppresses appetite

• serotonin = fenfluramine agonist

gasttic bypass surgery

• Roux-en-Y produces weight loss

• stomach is taken out of pathway

• person can only eat small foods

• gut microbes associated with obesity, microbial signals changed

alpha feto protein

• only females have it

• prevents masculinization in females

• binds estrogen

medial anterior nucleus of hypothalamus

• linked to lordosis

• lesion disrupts lordosis

• stimulation elicits proceptive behavior and lordosis

medial preoptic nucleus lesion

eliminate male sexual pattern in rats, stimulation triggers onset of sexual behavior

INAH-3

• interstitial nucleus of anterior hypothalamus

• human equivalent of rat’s sexually dimorphic nucleus

• larger in men than women, and straight men than gay men

amygdala lesion

blocks appetitive phase of sexual motivation (ex. rat does not work for access to female but does copulate if given her since consummatory motivation is still intact)

continuum vs. categorical view of sexuality

• first = linear organization, exists at two poles

• second = specific separations, overlap is possible, each identity is categorically unique

HPA axis

(hypothalamic, pituitary, adrenal) corticotrophin releasing factor/CRF is released when stress is turned on

• CRF in hypothalamus and amygdala goes down to pituitary → ACTH release → acts on adrenal gland → A secretes glucocorticoid stress hormone (cortisol)

common currency

• mesolimbic pathway

  • midbrain tegmentum to ventral striatum (*nucleus accumbens)

• dopamine and opioids

Olds & Milner study

• rats pressed lever to stimulate septum and LH (brain regions associated with rewarding feeling for rat) → pressed even if there was electric shock, indicating reward was potent enough to motivate overcoming negative consequence

• suggests that pleasure centers exist in the brain

lateral hypothalamus lesions

1. hunger → aphagia

2. sleep → contains hypocretin neurons which promote waking

3. septal rage & amygdala hierarchy → blocks all aggression

4. reward → blocked

aversive reaction

• conditioned taste aversion by pairing sweet taste with nausea

• implies that disgust is not just from bitterness— it can be conditioned

optogenetic stimulation of central amygdala

created wanting sensation in rats without liking (ex. maladaptive want for things that hurt was possible to condition in rats)

Lashley transection experiment

• right that cortex does not play major role in learning, but wrong about cortex being entirely equal/having mass action (specialization exists)

• lesions of cortex → impaired learning

• size of lesion determined impairment → larger lesion = larger deficit

• location of lesion irrelevant

aplysia and mammalian learning: similar or not?

yes because of long-term potentiation and hippocampus

hippocampal lesion and learning

does not block associative learning, but does inhibit complex learning

nucleus interpositus lesion

blocks eyeblink CR and learning of skilled habits

Bastian dolphin experiment

failure to use own recorded calls to help with task, performance was still at 50% accuracy